Field of the Invention
The present invention relates to an optical element manufacturing apparatus that manufactures an optical element.
Description of the Related Art
In recent years, improvements in performance and functioning of optical elements such as lenses, prisms, or mirrors have been required, and a method for improving performance by changing an optical surface shape to an aspherical shape is known, for example. In particular, in mass-producing an optical element having an aspherical shape, a manufacturing method for pressurizing a molding material that has been heated and softened by using a mold is employed.
There are needs for an optical element having a middle or large diameter. Therefore, it is necessary to cope with mass-production of optical elements having a middle or large diameter. Examples of an optical element manufacturing apparatus that is suitable to mass-produce an optical element which is not limited to the optical element having a middle or large diameter include the following.
An optical element manufacturing method for sequentially conveying a molding material housed in a mold set to respective stages for heating, pressurization, and cooling so as to manufacture a desired optical element is known. The mold set includes, for example, an upper mold, a lower mold, a drum mold, and the like. The drum mold is a cylindrical member that is positioned around the upper mold and the lower mold.
In the optical element manufacturing apparatus, plural pairs of upper and lower stage units are arranged so as to function as a heating stage, a pressurization stage, a cooling state, or the like.
A temperature control block is mounted onto the stage unit. The temperature of the temperature control block can be controlled, and the temperature control block is set to satisfy a condition for a corresponding process (a heating process, a pressurization process, or a cooling process).
A heating source and a temperature measurement unit are buried in the temperature control block. A method is employed for detecting a temperature at a prescribed position by usually using a plurality of cartridge type heaters as the heating source, and using a temperature sensor such as a thermocouple as the temperature measurement unit.
The temperature control block is connected to a control unit that functions as a temperature output adjustment device outside the stage unit. In the temperature control block, an output state of the heating source is adjusted according to a signal output from the temperature sensor such that a temperature state is controlled.
A method has been proposed for improving a temperature distribution by providing the temperature control block above with portions that respectively have a high watt density and a low watt density in a heater cartridge (see, for example, Japanese Laid-Open Patent Publication No. 2012-116705).